Vascular Plant Structure and Growth

Vascular Plant Structure, Growth, and Development

• Plants have a hierarchical organization of organs, tissues, and cells.

• Different meristems produce new cells for primary and secondary growth.

• Primary growth lengthens roots and shoots.

• Secondary growth increases the diameter of woody plants' stems and roots.

• Growth, morphogenesis, and cell differentiation shape the plant body.

• Structures fit function at the cellular, tissue, and organ levels in vascular plants:

  • Photosynthetic cells contain chloroplasts for energy conversion.
  • Leaves maximize sunlight absorption and gas exchange.
  • Dermal tissue protects organs.
  • Vascular tissue supports and transports materials.
  • Stems support leaves and maximize photosynthesis.
  • Roots anchor the plant and absorb water and minerals.
  • Root hairs increase water and mineral absorption surface area.
  • Tube-shaped cells transport water and minerals or sugars.
  • Ground tissue carries out photosynthesis and stores sugars.

• Roots: Anchor plants, absorb minerals and water, store carbohydrates.

  • Primary root emerges from embryo.
  • Lateral roots branch from primary root.
  • Taproot system has one main root.
  • Fibrous root system has a thick mat of slender roots.
  • Root hairs increase surface area for absorption.

• Stems: Support leaves, elevate reproductive structures, sometimes photosynthesize.

  • Alternating nodes and internodes.
  • Apical buds are concentrated shoot tips.
  • Axillary buds are in leaf axils, can form branches or flowers.
  • Modified stems also exist for storage or asexual reproduction (rhizomes, stolons, tubers).

• Leaves: Main photosynthetic organs, exchange gases with atmosphere.

  • Leaf blade and petiole.
  • Parallel veins in monocots, branched veins in eudicots.
  • Simple leaves have undivided blades; compound leaves have leaflets.
  • Spines, tendrils, storage leaves.

• Tissues: Dermal (protection), vascular (transport), ground (metabolism).

  • Dermal: epidermis (protection) cuticle (water retention) periderm (woody plants).
  • Vascular: xylem (water transport), phloem (sugar transport).
  • Ground: pith, cortex (storage, photosynthesis, support)

• Different Meristems: Apical (length), lateral (thickness):

  • Apical: at root and shoot tips, generates primary growth.
  • Lateral: vascular cambium (secondary xylem/phloem), cork cambium (periderm).

• Secondary Growth: Increases stem & root diameter.

  • Vascular cambium adds secondary xylem (wood) and phloem.
  • Cork cambium produces periderm, replacing epidermis.

• Evolutionary Adaptations: (of roots, stems, and leaves)

  • Buttress, prop roots for support
  • Pneumatophores for oxygen in swamps
  • Storage roots (e.g. beets, carrots)
  • Tendrils for climbing
  • Spines for defense
  • Thick, waxy surfaces for water retention

• Flower Development & Cell Differentiation: controlled by genetic mechanisms involving specific genes (e.g., ABC genes) & environmental signals such as day length. Includes patterns of organ formation & development, including diverse floral structures. Mutations can result in abnormal or altered flower development with differing ratios of flower parts.

• Leaf Features & Function: influence of environment (like temperature or rainfall) on leaf structure (& e.g., toothiness of leaves) to adapt for photosynthesis & water conservation.

• Water-Conducting Cells of the Xylem: Tracheids & vessel elements, dead at maturity, with lignin-thickened walls for support. Perforation plates allow water flow efficiently between cells.

• Sugar-Conducting Cells of the Phloem: Sieve tube elements (alive at maturity), companion cells, sieve plates. They transport sugars from the source to the sink (areas of storage or growth).

• Primary Growth elongation of plants, roots, and shoots, through apical meristems (the dividing cells).

• Secondary Growth increase in diameter of woody plants, through lateral meristems (vascular cambium & cork cambium).

• Dendrochronology: Using tree ring patterns to study climate change and past environmental conditions.